...how do you explain the dissenters' concern that they had just said he could be president?
Where exactly do you read that he could be President?
"Considering the circumstances surrounding the framing of the Constitution, I submit that it is unreasonable to conclude that 'natural-born citizen' applied to everybody born within the geographical tract known as the United States, irrespective of circumstances, and that the children of foreigners, happening to be born to them while passing through the country, whether of royal parentage or not, or whether of the Mongolian, Malay or other race, were eligible to the Presidency, while children of our citizens, born abroad, were not."
Considering it starts with: Considering the circumstances surrounding the framing of the Constitution
Another attempt at a then-means-the-same-as-now analogy like you pointed out previously with Rawle, perhaps?